Brian uses a logging system to display warnings and general information messages
to the user, as well as writing them to a file with more detailed information,
useful for debugging. Each log message has one of the following “log levels”:

ERROR

Only used when an exception is raised, i.e. an error occurs and the current
operation is interrupted. Example: You use a variable name in an equation
that Brian does not recognize.

WARNING

Brian thinks that something is most likely a bug, but it cannot be sure.
Example: You use a Synapses object without any synapses in your
simulation.

INFO

Brian wants to make the user aware of some automatic choice that it did for
the user. Example: You did not specify an integration method for a
NeuronGroup and therefore Brian chose an appropriate method for you.

DEBUG

Additional information that might be useful when a simulation is not working
as expected. Example: The integration timestep used during the simulation.

DIAGNOSTIC

Additional information useful when tracking down bugs in Brian itself.
Example: The generated code for a CodeObject.

By default, all messages are written to the log file and all messages of level
INFO and above are displayed on the console. To change what messages are
displayed, see below.

Note

By default, the log file is deleted after a successful simulation run,
i.e. when the simulation exited without an error. To keep the log around,
set the logging.delete_log_on_exit preference to False.

You can also change details of the logging system via Brian’s Preferences
system. With this mechanism, you can switch the logging to a file off completely
(by setting logging.file_log to False) or have it log less messages (by
setting logging.file_log_level to a level higher than DIAGNOSTIC) – this
can be important for long-running simulations where the log might otherwise take
up a lot of disk space. For a list of all preferences related to logging, see the
documentation of the brian2.utils.logger module.

Warning

Most of the logging preferences are only taken into account during
the initialization of the logging system which takes place as soon as brian2
is imported. Therefore, if you use e.g. prefs.logging.file_log=False in
your script, this will not have the intended effect! Instead, set these
preferences in a file (see Preferences).